Pre-season has officially begun with several Arsenal players having returned to the club, but Mikel Arteta’s squad is still not all together. A number of first-team Arsenal stars returned to London Colney yesterday for the first day of pre-season. For many, this was not in fact the true start of their preparations for the new campaign. Earlier in the summer, Mikel Arteta hosted a training camp in Marbella. Arsenal captain Martin Odegaard has already discussed the positive impact that their time in the Spanish coastal city had. Odegaard was amongst those in training again yesterday, along with …